System and method for occupancy sensing using adjustable detection and load control profile

ABSTRACT

An occupancy sensor is disclosed including a passive infrared (PIR) sensing element, a temperature sensing element, and a processor. The processor receives temperature signals from the temperature sensing element and configures the occupancy sensor into a selected operating mode based the received temperature signal. The operating mode may be associated with a predetermined sensing threshold of the PIR sensing element. The processor controls an associated load based on the selected operating mode and the received occupancy signals. The occupancy sensor can alternatively include an occupancy sensing element and a photodetector. Based on the amount of light detected by the photodetector over time, the occupancy sensor can calculate a rough estimate of time of day, and can automatically adjust one or more sensing and/or operational characteristics based on that time of day determination. A photosensor may implement daylight harvesting based on different light levels associated with different times of day.

FIELD OF THE DISCLOSURE

The present disclosure relates generally to occupancy sensing systems,and more particularly to an improved system and method for occupancysensing systems having adjustable detection profiles.

BACKGROUND OF THE DISCLOSURE

Occupancy sensors are designed to save energy by detecting the presenceof a moving object in an area of coverage and switching a load (e.g., alight source, an HVAC system, etc.) on and off depending upon thepresence of the moving object. For example, when motion is detectedwithin the area of coverage, the load is turned on. Alternatively, whenmotion is not detected within the area of coverage, thus indicating thatthe area of coverage is not occupied, the load is turned off after apredetermined period of time. Occupancy sensors thus facilitateelectrical energy savings by automating the functions of, for example, alight switch.

Occupancy sensors using passive infrared detection (PIR) have beenemployed in a variety of indoor applications with much success. PIRoccupancy sensors operate by sensing a body having a heat signature inexcess of background infrared (IR) levels. Since PIR occupancy sensorsrely on body heat detection, indoor applications that experience limitedtemperature extremes are a near perfect environment, and the indoor PIRoccupancy sensor can be easily tuned and tailored to identify body heatfrom the ambient temperature environment.

Although PIR occupancy sensors have also been used in outdoorapplications, the ability to accurately detect the temperature producedby a human body or an automobile within a wide range of ambienttemperatures is made more difficult. One reason for this, is because asthe ambient temperature of a monitored area rises, the differencebetween human body temperature and the ambient temperature decreases,and as a result PIR occupancy sensors can be less able to differentiatethe heat signature of a human body from the background heat signature ofthe surroundings. In addition, detection problems increase when road orparking surface temperatures rise, making it even more difficult for thePIR occupancy sensor to discern the heat signature of a moving objectfrom the background heat signature of the road or parking surface.

Prior occupancy sensing systems also suffer from deficiencies in thatthey do not adequately take into account time of day. More particularly,prior outdoor occupancy sensing systems have thus far not had thecapability to customize operation based on time of day so as to provideoptimum energy savings during periods when low activity is expected.

SUMMARY OF THE DISCLOSURE

In view of the aforementioned issues, an occupancy sensor is disclosedthat automatically adjusts its sensitivity and/or other operationalcharacteristics based on at least one sensed environmental factor. Inone embodiment, the environmental factor is ambient temperature, whilein other embodiments, the environmental factor can be the time of day.In this way the occupancy sensor can maximize its own performance andcan optimize operation of a lighting system in response to changingenvironmental factors.

An occupancy sensor is disclosed, including a passive infrared (PIR)sensing element, a temperature sensing element and a processor coupledto the PIR sensing element and the temperature sensing element. Theprocessor may be configured to receive temperature signals from thetemperature sensing element and configure the occupancy sensor into aselected one of a plurality of operating modes based on the receivedtemperature signals. The processor may further be configured to receiveoccupancy signals from the PIR sensing element and to control anassociated load based on the selected operating mode and the receivedoccupancy signals.

An occupancy sensor is disclosed, including an occupancy sensingelement, a photodetector, and a processor coupled to the occupancysensing element and the photodetector. The processor may be configuredto receive light signals from the photodetector and to configure theoccupancy sensor into at least one of a plurality of operating modesbased on an estimated time of day. The estimated time of day may bedetermined by the processor based on selected ones of said light signalsreceived from the photodetector. The processor may be configured toreceive occupancy signals from the occupancy sensing element and tocontrol an associated load based on the selected operating mode and thereceived occupancy signals.

A method is disclosed for controlling a load with an occupancy sensor.The method may comprise: at a PIR sensor, identifying an occupiedcondition of a monitored area and sending an occupancy signal to aprocessor; at a temperature sensing element, identifying an ambienttemperature of the monitored area and sending a temperature signal tothe processor representative of said ambient temperature; at theprocessor, receiving the temperature signal and configuring theoccupancy sensor into a selected one of a plurality of operating modesbased thereon; and controlling a load associated with the monitored areabased on the selected operating mode and the occupancy signal. Theselected operating mode may be associated with a predetermined sensingthreshold associated with the PIR sensor.

A method is disclosed for controlling a load with an occupancy sensor.The method may include: at an occupancy sensing element, identifying anoccupied condition of a monitored area and sending an occupancy signalto a processor; at a photodetector, identifying an ambient light levelof the monitored area and sending a light signal to the processorrepresentative of said ambient light level; at the processor, receivingthe light signals from the photodetector and configuring the occupancysensor into at least one of a plurality of operating modes based on anestimated time of day, the estimated time of day determined by theprocessor based on selected ones of said light signals received from thephotodetector; and controlling a load associated with the monitored areabased on the selected operating mode and the occupancy signal.

BRIEF DESCRIPTION OF THE DRAWINGS

By way of example, a specific embodiment of the disclosed device willnow be described, with reference to the accompanying drawings, in which:

FIG. 1 is a schematic diagram of an exemplary occupancy sensing systempositioned to monitor an outdoor area;

FIG. 2 is a schematic of an occupancy sensor according to thedisclosure;

FIG. 3 is a logic diagram illustrating an exemplary embodiment of thedisclosed method;

FIG. 4 is a logic diagram illustrating another exemplary embodiment ofthe disclosed method; and

FIG. 5 is a schematic of a daylighting system for monitoring an indooror outdoor area.

DETAILED DESCRIPTION

The disclosed system and method may find use in lighting controlsystems, which, in some embodiments, are outdoor lighting controlsystems. In exemplary embodiments, a PIR occupancy sensor can befine-tuned for best performance by modifying the pre-processing and/orpost-processing of a signal from a PIR sensing element in response tochanges in ambient temperature. In other embodiments, an occupancysensor can sense changes in daylight that occur near sunset and sunrisein order to estimate a close approximation of time of day, and can usethis estimation to vary operational parameters of the occupancy sensor.Non-limiting examples of operational parameters include, but are notlimited to, time delay before turning off an associated load andsensitivity adjustment thresholds.

FIG. 1 shows an exemplary outdoor application in which an occupancysensor 1 is mounted on an upper region of a light pole 2 so that thesensor can monitor a portion 4 of a parking lot 6 illuminated by one ormore lights 5. Although a single occupancy sensor 1 is illustrated, itwill be appreciated that multiple occupancy sensors 1 can be used inactual application to cover an entire monitored area, such as a largeparking lot. In addition, although the description will generallyproceed in relation to an occupancy sensor 1 having a PIR based sensingelement, it will be appreciated that one or more of the disclosedembodiments can alternatively or additionally include other types ofsensing elements now or hereinafter known, such as radio frequency (RF),ultrasonic, audio, video and the like as well as combinations thereof.

It will also be appreciated that the disclosed occupancy sensor 1 is notlimited to light pole installations, and thus the occupancy sensor 1 maybe mounted on any of a variety of surfaces including walls and ceilings.Examples of appropriate mounting arrangements include wall-mounting withthe occupancy sensor positioned to monitor alleys, driveways, enclosedcourtyards, and the like. Ceiling mounting arrangements can also beused, for example, in outdoor parking garage applications.

Referring now to FIG. 2, the occupancy sensor 1 may include a passiveinfrared (PIR) sensing element 8, a temperature sensing element 10,memory 16, a load controller 18, and a processor 12. In addition, theoccupancy sensor 1 may include a photodetector 14. The memory 16 may beassociated with the processor 12 for storing instructions, look uptables, operational history data and the like. The memory 16 may be anyof a variety of volatile or non-volatile memory devices now orhereinafter known by those of ordinary skill in the art. The loadcontroller 18 may be operatively coupled to one or more loads 20 such asthe lights 5 illustrated in FIG. 1. Based on information provided to theprocessor 12 from the PIR sensing element 8, the processor 12 mayinstruct the load controller 18 to energize the one or more loads 20.The processor 12 may also command the load controller 18 to de-energizethe one or more loads 20 a predetermined amount of time after occupancywithin the area of coverage is no longer detected.

Although the illustrated embodiment shows all of the operative elements(PIR sensing element 8, temperature sensing element 10, et al.) as beinginternal to the occupancy sensor 1, it will be appreciated that some orall of these operative elements can be located external to and/orseparate from the occupancy sensor. For example, such an arrangement maybe appropriate when using an analog PIR sensing element 8. In suchcases, the temperature sensing element 10 may be any appropriatetemperature sensing device such as a thermocouple, a resistancetemperature detector (RTD), a thermistor, or the like. When using adigital PIR sensing element 8, however, the digital PIR sensor itselfmay provide the desired temperature data for use by the processor 12,and thus a discrete temperature sensing element 10 may not be required.It will also be appreciated that the disclosed load controller 18 may ormay not be incorporated into the housing of the occupancy sensor 1. Forexample, the occupancy sensor 1 may be a low-voltage occupancy sensorthat works in combination with a power pack, as will be readilyappreciated by one of ordinary skill in the art.

The photodetector 14 may employ any of a variety of appropriate lightsensing technologies, including active pixel sensors, photoresistors,charge coupled devices, and the like. The load controller 18 may be arelay or other arrangement or device appropriate for controlling theenergizing and de-energizing of the associated load 20. In theillustrated embodiment, the load controller 18 may communicate with theexternal load 20 along a wired or wireless communications channel 22.

In some embodiments, the sensor 1 may be coupled to a private or publicnetwork to allow occupancy information to be transferred to a remotecomputer and/or facility. In some embodiments, occupancy information maybe sent via the Internet to a web page to enable remote monitoring ofthe associated area. A building manager, lot manager, or otherauthorized individual or agency may monitor this information to enableeasy access to occupancy data. Communication between the sensor 1 andthe building manager (or other user) via a private or public network ordirect connection can be via any of a variety of appropriate hard-wiredor wireless connections.

As previously noted, in some embodiments the occupancy sensor 1 can befine-tuned for best performance by modifying pre-processing and/orpost-processing of the signal from the PIR sensing element 8 in responseto environmental changes in ambient temperature and/or daylight sensedby the temperature sensing element 10 and/or the photodetector 14. Thus,the occupancy sensor 1 may have one or more operating profilescorresponding to different sensed environmental conditions.

For example, based on temperature information provided by thetemperature sensing element 10, the processor 12 can adjust a sensingthreshold required to transmit a detection signal to the load controller18. As will be understood, PIR occupancy sensors operate by sensing anobject having a heat signature in excess of background infrared (IR)levels. That is, PIR sensors observe a difference in temperature betweenthe object and the background and they register that as a change.Depending on the magnitude of this change, logic built into the PIRoccupancy sensor 1 either ignores the change if it is below a certainthreshold, or causes a detection signal to be issued if the change isabove the threshold required to signify an occupied condition. As theambient temperature of a monitored area rises, the difference betweenthe object (human body, vehicle, etc.) temperature and the ambienttemperature decreases, and as a result PIR occupancy sensors can be lessable to differentiate the heat of an object from the heat of thesurroundings. As previously noted, this problem may be particularlyacute where the occupancy sensor is deployed in a hot climate where thetemperature of the monitored area can be very high.

In one non-limiting exemplary embodiment, the processor 12 can useinformation from the temperature sensing element 10 to adjust a sensingthreshold so that a greater or lesser temperature differential betweenthe monitored area and a sensed object must be exceeded before anoccupied condition is signaled and the load 20 is energized. In oneembodiment, as the temperature of the monitored area increases (assensed by the temperature sensing element 10), the processor 12decreases the temperature differential required to signal an occupiedcondition. Different predetermined threshold sensitivities may beassociated with different operating modes of the occupancy sensor 1. Theoccupancy sensor 1 may include a plurality of such modes of operationdepending upon the particular environment in which the occupancy sensoris installed.

In addition, other parameters of the occupancy sensor 1, such as timedelay, can be modified based on directly sensed conditions (e.g.,temperature) or indirectly determined conditions (e.g., time of day). Inone non-limiting exemplary embodiment, it may be desirable to increasethe time delay before turning off an associated load during periods inwhich ambient temperature is above a predetermined value, and wheretemperature sensing of an occupied condition may be less reliable.

In one non-limiting exemplary embodiment, the processor 12 employs analgorithm to adjust this threshold. In other embodiments, adjustmentvalues are provided in a lookup table in the non-volatile memory 16associated with the processor 12. Adjustment values may alternatively bestored in a look up table associated with the processor 12 in lieu ofseparate non-volatile memory. In yet another embodiment (not shown), thethreshold adjustment may be manually entered via a user input devicesuch as a dip switch, trim pot, rotary switch, touch pad, touch screen,or the like.

In addition, or alternatively, ambient temperature sensed by thetemperature sensing element 10 can be used to estimate a time of day,and this estimate can be used to adjust operating parameters of theoccupancy sensor. For example, during daylight hours the temperaturesensing element 10 can send signals to the processor 12 indicative of adaylight condition. In one embodiment, if the temperature sensingelement 10 senses a particular discrete temperature or a predefinedupward trend in temperature it may associate that with sunrise. A sensedcounter-trend or discrete temperature value may be associated withsunset. Upon receiving a signal (or signals) from the temperaturesensing element 10 indicative of daytime, the processor 12 may act toprevent the load controller 18 from energizing the load 20 regardless ofwhether the PIR sensor 8 senses an occupied condition of the monitoredarea. Such an arrangement may be useful in conserving energy, since itis needless to turn on outdoor lights in the daytime as an indication ofthe area's occupation status. As will be appreciated, other sensorsettings such as sensitivity, and time-delay before turning off anassociated load, can be adjusted in a similar manner, as desired.

During twilight, or after it has become dark, the temperature (ortemperature trend) sensed by the temperature sensing element 10 may dropbelow a predetermined threshold, which may be indicative of sunset.Thus, upon receiving such a signal (or signals) from the temperaturesensing element 10 the processor 12 may enable the load controller 18 toenergize the associated load 20 if the PIR sensor 8 senses an occupiedcondition of the monitored area.

An exemplary method of using the disclosed system 1 will now bedescribed in relation to FIG. 3. At step 100 the temperature sensingelement 10 associated with the occupancy sensor 1 may send datarepresentative of ambient temperature to the processor 12. It will beappreciated that this data may be sent substantially continuously, or atlonger periodic intervals. At step 110, the processor 12 may compare thereceived data to one or more threshold values. In one non-limitingexemplary embodiment, the threshold values are stored in memory 16. Atstep 120, if the received data is determined to exceed a first thresholdvalue, the processor 12 may configure the occupancy sensor 1 into afirst operating mode in which a sensing threshold associated with thePIR sensor 8 is set to a first value. In one non-limiting exemplaryembodiment, this first threshold value corresponds to an ambient lightlevel associated with a first predetermined time of day. At step 130, ifthe received data is determined to exceed a second threshold value,which is higher than the first threshold value, the processor 12 mayconfigure the occupancy sensor 1 into a second operating mode in which asensing threshold associated with the PIR sensor 8 is set to a secondvalue that is different from the first value. In one non-limitingexemplary embodiment, this second threshold value corresponds to anambient light level associated with a second predetermined time of daywhich is different from the first predetermined time of day. At step140, if the received data is determined to exceed a third thresholdvalue which is higher than the first and second threshold values, theprocessor 12 may configure the occupancy sensor 1 into a third operatingmode in which a sensing threshold associated with the PIR sensor 8 isset to a third value that is different from the first and second values.In one non-limiting exemplary embodiment, this third threshold valuecorresponds to an ambient light level associated with a thirdpredetermined time of day which is different from the first and secondpredetermined times of day. This process can continue depending upon thetotal number of the threshold values stored in memory (or otherwiseassociated with the processor 12). This process can run continuously, orit can be repeated at discrete periodic intervals, as desired.

As previously noted, the occupancy sensor 1 may additionally, oralternatively, be configured to sense environmental changes other thantemperature, and may change one or more operational characteristics ofthe occupancy sensor based thereon. For example, the occupancy sensor 1may sense the time of day, and may automatically adjust operation of theoccupancy sensor in response.

As previously noted, in some commercial environments, such as parkinglots, time of day performance changes of an occupancy sensor 1 can behighly desirable. For example, immediately after sunset, lighting in themonitored area (e.g., a parking lot) may stay on for 30 minutes aftermotion is detected for the convenience of the business customers (i.e.,so they can walk safely from their car to the store, and vice versa).However, at a later time, say for example, beginning at 10:00 pm throughsunrise, the lighting may stay on for only a few minutes (e.g., 5minutes) after motion is detected to save energy, since few if anycustomers will be in the parking lot. This short period of illuminationis also sufficient for security personnel to detect whether a person ismoving through the parking lot.

It can be difficult, however, to maintain a synchronized real time clockin pole or ceiling mounted occupancy sensors 1. Thus, in accordance withthe disclosure a rough estimation of the time of day can be determinedby the occupancy sensor 1. In one non-limiting exemplary embodiment,this can be achieved by sensing the ambient light level (using thephotodetector 14) and identifying changes in daylight that occur nearsunset and sunrise to determine an estimation of the midpoint betweensunset and sunrise (i.e., midnight). This estimation is expected to bewithin about one hour (+/−) from actual midnight, and can be used by theoccupancy sensor 1 as a baseline for determining an estimated time ofday. The estimated time of day can then be used by the processor 12 tovary parameters such as time delay (i.e., the amount of time a loadstays energized), sensitivity of the occupancy sensor 1 and the like.

Thus, in one embodiment, the photodetector 14 can monitor the ambientlight level, and can send representative signals to the processor 12.The processor 12 can use the signals received from the photodetector 14to determine an approximate sunrise time and an approximate sunset time,and from that information the processor can determine an estimatedmidnight value (again, within an acceptable tolerance). From thatestimated midnight value, the processor 12 may implement certainoperational modes based on the estimated time of day.

The occupancy sensor 1 may thus have at least three operational modes.The first mode may be employed during normal daylight hours, the secondmode may be employed for an early portion of the evening hours when itis dark outside but when businesses are still operating, and the thirdmode may be employed for a later portion of the evening hours when it isdark outside and businesses are no longer operating. As will beappreciated, exterior lighting needs may be different during each ofthese periods.

Thus, when the photodetector 14 senses light above a predeterminedthreshold (associated with the daylight hours), the processor 12 mayplace the occupancy sensor 1 in the first mode. In this first mode theprocessor 12 may operate to prevent the load controller 18 fromenergizing the load 20 regardless of whether the PIR sensor 8 detectsmotion in the monitored area.

When the photodetector 14 senses light below a predetermined threshold(associated with sundown or twilight), the processor 12 may placeoccupancy sensor 1 in the second mode. In this second mode, theprocessor 12 may function such that when the PIR sensor 8 detects motionin the monitored area, the load controller 18 is commanded to energizethe load 20. The load 20 may then be maintained in the energized statefor a first predetermined time period, for example 30 minutes aftermotion is detected. This first predetermined time period may besufficient that business employees or customers can safely exit thestore and walk to their car, and vice versa.

The occupancy sensor 1 can be programmed to enter the third mode whenthe processor 12 determines that a predetermined hour of day has beenreached. As previously noted, this predetermined hour of day can bebased on the estimated midnight value. For example, if the user electsto have the occupancy sensor 1 enter the third mode at the predeterminedtime of 10:00 PM, the processor 12 can be programmed to determine thistime as being two hours prior to the estimated midnight value. Thus,when the processor 12 determines the time to be 10:00 PM, the occupancysensor 1 can be placed in the third mode. In this third mode theprocessor 12 may function such that when the PIR sensor 8 detects motionin the monitored area, the load controller 18 is commanded to energizethe load 20. The load 20 may be maintained in the energized state for asecond predetermined time period which is less than the firstpredetermined time period. In one non-limiting exemplary embodiment,this second predetermined time period can be about 5 minutes. Thissecond predetermined time period can be long enough to enable securitypersonnel to identify the presence of a person or a vehicle in themonitored area, but is not so long that the lights are left on for anexcessive amount of time, thus saving energy.

In one embodiment, the desired time of day for entering this third mode,as well as the first and second time periods, can be programmed into theprocessor 12. Alternatively, these values can be manually entered intothe occupancy sensor 1 via a user input device such as a dip switch,trim pot, rotary switch, touch pad, touch screen or the like (notshown).

When the photodetector 14 once again senses light above a predeterminedthreshold (associated with the daylight hours), the processor 12 mayplace the occupancy sensor 1 in the first mode. The process can continuefrom there.

In some embodiments the processor may periodically (e.g., daily) updateits estimation of midnight based on light levels sensed by thephotodetector 14. In other embodiments this value may be obtained onlyonce, or at another discrete period such as monthly or quarterly.

It will be appreciated that for applications in which multipleindividual occupancy sensors 1 are used to monitor an area, eachoccupancy sensor 1 can have its own arrangement of photodetector 14,processor/circuitry 12, as well as its own programmed behavior. Thus,each occupancy sensor 1 in a group can independently determine time ofday, and can modify operation of an associated load 20 based on thatdetermined time of day. Alternatively, where multiple individualoccupancy sensors 1 are used to monitor an area, one or more of theoccupancy sensors may independently determine time of day, and thisinformation may be populated to the other occupancy sensors in thegroup.

A non-limiting set of examples of different characteristics that can beimposed during these different operational modes, include changes insensitivity of the PIR sensor 8 (i.e., to accommodate for changes inambient temperatures), changes in the processing of the signal from thePIR sensor, filtering the signal from the PIR sensor to look fordifferent types of signatures, and time delay (i.e., time the loadremains energized before turning off). For example, as the sensorbecomes less reliable (i.e., less able to reliably detect the presenceof a human heat signature), the “time on” setting for the associatedload may be extended.

An exemplary method of using the disclosed system 1 will now bedescribed in relation to FIG. 4. At step 200, the photodetector 14associated with the occupancy sensor 1 sends data representative of anambient light level to the processor 12. It will be appreciated thatthis data may be sent substantially continuously, or at longer periodicintervals. At step 210, the processor 12 may compare the received datato one or more threshold values. In one non-limiting exemplaryembodiment, the threshold values are stored in memory 16. At step 220,if the received data is determined to exceed a first threshold value,the processor 12 configures the occupancy sensor 1 into a firstoperating mode in which the load 20 is not energized regardless ofwhether the PIR sensor 8 senses an “occupied” condition (i.e., one inwhich the PIR sensor senses a body having a heat signature in excess ofIR levels) in the monitored area. In one non-limiting exemplaryembodiment, this first threshold value corresponds to an ambient lightlevel associated with a first predetermined time of day. At step 230, ifthe received data is determined to be below a second threshold value,which is lower than the first threshold value, the processor 12configures the occupancy sensor 1 into a second operating mode in whichthe load 20 is energized when the PIR sensor 8 senses an “occupied”condition (i.e., one in which the PIR sensor senses a body having a heatsignature in excess of IR levels. In one non-limiting exemplaryembodiment, the second threshold value corresponds to an ambient lightlevel associated with a second predetermined time of day that isdifferent from the first predetermined time of day. In this secondoperating mode, the load 20 may be maintained in the energized state fora first predetermined time period. In one non-limiting exemplaryembodiment, this first predetermined time period may be about 30minutes. At step 240, the processor 12 determines that a predeterminedtime of day has been achieved, and configures the occupancy sensor 1into a third operating mode in which the load 20 is energized when thePIR sensor 8 senses an “occupied” condition (i.e., one in which the PIRsensor senses a body having a heat signature in excess of IR levels). Inthis third operating mode, the load 20 may be maintained in theenergized state for a second predetermined time period that is less thanthe first predetermined time period. In one non-limiting exemplaryembodiment, this second predetermined time period may be about 5minutes. At step 250, if the received data is determined to exceed afirst threshold value, the processor 12 configures the occupancy sensor1 back into the first operating mode.

Although the illustrated occupancy sensor 1 includes a discreteprocessor 12, it will be appreciated that the appropriate logic forimplementing the disclosed features of this sensor may also be embodiedin appropriate hardwired circuitry. Thus, the logic associated with thisembodiment can be in hardware, software, or a combination of the two. Itwill be appreciated that the term “processor” in this application shouldbe interpreted to be a discrete processor or hardwired circuitryconfigured to perform the same or similar function.

Some of the inventive principles of the disclosure relate to techniquesfor occupancy sensing, in particular, for sensing the presence or motionof a person or a moving object in an area of interest. In oneembodiment, lighting levels can be adjusted in or about the area ofinterest responsive to sensing the person or moving object. In anotherembodiment, a security alarm can be triggered responsive to sensing theperson or moving object.

Referring now to FIG. 5, an embodiment will be described in which aphotodetector can be employed to implement a variable daylightingfeature in which lighting levels are adjusted in a monitored areadepending upon the time of day. Photodetectors can be used to monitortask or ambient light levels in a monitored area as part of an energymanagement system. Thus, the brightness of powered lights in aparticular area can be adjusted so that a total amount of light (i.e.,natural light plus powered light) in an occupied area meets one or moreuser-defined levels. In one embodiment, if the photodetector detects alight level in the area to be less than a user defined minimum, then thepowered lights can be brightened to increase the light level to thedesired minimum value. Likewise, if the photodetector detects a lightlevel in the area to be greater than the user defined minimum, then thepowered lights can be dimmed to decrease the light level to the desiredminimum value. Energy savings can be achieved using this scheme. Forexample, it may be desirable to have a lower target light level valuefor “daylighting” during after-hours as compared to working hours. Suchan arrangement can save more energy than prior systems that include asingle target light level value that is applied to an entire 24 hourperiod. The disclosed system and method may utilize different photocelltarget lighting levels based on time of day, day of the week, or othercriteria to achieve this desired energy savings.

Photodetectors can be suitable for installation in rooms with windowsand open areas receiving substantial ambient light. They may also beemployed in a variety of outdoor working environments. In application,one or more photodetectors can be connected to a load control devicethat can control operation of one or more associated loads (e.g.,lights) in response to detected light levels. The load control devicecan control the loads using on/off signaling, dimming and the like.

In some embodiments the photodetector can measure ambient light in aspecified area, and can send signals representative of light level tothe load control device which, in turn, can adjust the loads (e.g.,lighting fixtures) to maintain a constant lighting level in themonitored area. As mentioned, in some embodiments, this can cause thelights in the monitored area (with windows, skylights or other sourcesof ambient light) to automatically brighten or dim depending on how muchlight the photodetector detects. The desired constant lighting level canbe programmed into a processor associated with the load control device,and thereafter the load control device can receive the photodetector'sreal-time light measurement (or a signal representative thereof) and canadjust the associated lighting load(s) to maintain a steady lightinglevel within the monitored area.

As will be described in greater detail later, if the measured lightlevel in a specified area is determined by the photodetector (orprocessor) to be equal to a predetermined user-defined light level, thenthe lighting loads serving the specified area are controlled to remainat a constant lighting level. By contrast, if the measured light levelis determined to be less than the predetermined user-defined lightlevel, then the lighting loads can be controlled to brighten until themeasured light level equals the predetermined user-defined light level.Finally, if the measured light level is determined to be greater thanthe predetermined user-defined light level, then the loads may be dimmeduntil the measured light level equals the predetermined user-definedlight level.

FIG. 5 illustrates a system 23 including an exemplary photodetector 24coupled to a processor 26 and a load control device 28. The load controldevice 28 can, in turn, can be coupled to one or more loads 30, such aslighting fixtures. It will be appreciated that although it is shown as aseparate element, the processor 26 may instead be integral to thephotodetector 24 or the load control device 28, or it may be part of anassociated occupancy sensor (not shown). It will also be appreciatedthat although the photodetector 24 is shown as a stand-alone element, itcan, in some embodiments, be provided in conjunction with, or as partof, an occupancy sensor such as the occupancy sensor 1 disclosed inrelation to the previous embodiments.

The load control device 28 can include appropriate dimming circuitry tofacilitate dimming of one or more of the connected loads 30 in responseto commands received from the processor 26.

The photodetector and processor may receive power from the load controldevice 28 via a power line 32, and may transmit load control signals tothe load control device 28 via a signal line 34. In response to signalsreceived from the photodetector 24, the load control device 28 mayadjust power supplied to the load 30 via one or more power lines 36. Inone embodiment, the load 30 may include at least one light. The loadcontrol device 28 may receive line power from a building power source38. A wall switch 40 may further be provided to control an on/off statusof the load 30.

In addition, the processor 26 may have a connection to a buildingmanagement system (BMS) 42 via a wireless or hardwired communicationslink 44. The building management system 42 may be used to monitor statusand operation of the system 23 by building personnel. The BMS 42 mayalso be used to remotely reconfigure the target light levels of thesystem 23.

In one embodiment, the photodetector 24 may be configured to send asignal to the processor 26 when a light level that is above or below thepredetermined threshold is sensed. In another embodiment, thephotodetector 24 may continuously sends light level signals to theprocessor 26, and the processor 26 may determine if the sensed lightlevel is above or below the predetermined threshold.

Although the illustrated embodiments include a single photodetector 24,a single load control device 28, and a single load 30, it will beappreciated by those of ordinary skill in the art that any number ofsensors, loads and/or load control devices may be used in combination toprovide a lighting control system having a desired functionality andcoverage.

As noted, the photodetector 24 may be operable to sense an ambientlighting level in a monitored area and to provide an associated lightinglevel signal to the processor 26. Based on this lighting level signal,the processor 26 may command the load control device 28 to adjust thebrightness of one or more of the connected loads 30. In one embodiment,a plurality of predetermined ambient lighting levels may be stored innon-volatile memory 27 associated with the processor 26, and theprocessor may compare the lighting level signal from the photodetector24 to determine if the measured ambient light level in the monitoredarea is at or above a predetermined level. The memory 27 may be any of avariety of volatile or non-volatile memory devices now or hereinafterknown by those of ordinary skill in the art. In some embodiments, thesystem of FIG. 5 can be implemented with an occupancy sensor such as,but not limited to, the occupancy sensor 1 disclosed in relation to theprevious embodiments.

In an exemplary embodiment, the system of FIG. 5 may be used toimplement lighting control for an area using a plurality of differenttarget lighting levels, where the plurality of different target lightinglevels are associated with particular times of day and/or days of theweek. For example, a first predetermined target lighting level may beassociated with the time range of from 8:00 AM to 5:00 PM. A secondpredetermined target lighting level may be associated with a time rangeof from 5:00 PM to 6:00 PM (i.e., after normal working hours, but beforethe area is vacated). Thus, the second predetermined target lightinglevel may be lower than the first predetermined target lighting level. Athird predetermined target lighting level may be associated with a timerange of from 6:00 PM to 8:00 AM (i.e., when the area is expected to beunoccupied). Thus, the third predetermined target lighting level may belower than the first and second predetermined target lighting levels.Fewer or greater numbers of such levels may be used. In addition, thelevels may be modified based on the day of the week, holidays, plannedbusiness closures, and the like.

In non-limiting exemplary embodiments, the first predetermined targetlighting level for a warehouse environment can be about 30 foot-candles(ft-c), while the first predetermined target lighting level for anoffice space may be about 40 ft-c. The second predetermined targetlighting level for a warehouse environment can be between about 30 ft-cand about 15 ft-c, while the second predetermined target lighting levelfor an office space may be between about 40 ft-c and about 15 ft-c. Thethird predetermined target lighting level may be about 15 ft-c for bothwarehouse and office spaces.

It will be appreciated that the disclosed control technique may find usein areas such as office or warehouse areas where it may be desirable tomaintain the lighting level in the area at a first, higher, level duringworking hours, at a second, lower level during the hour after work toenable people to get out of the workplace safely, followed by a third,even lower, value at night, on the weekends and holidays when theworkplace is expected to be unoccupied.

The aforementioned predetermined target lighting levels may be based ontime of day as estimated by the embodiment described in relation toFIGS. 1-4. Alternatively, time of day information may be provided by anexternal clocking source associated with the processor 25, provided bythe BMS 42 via communications link 44.

As previously noted, the photodetector 24 and system 23 can be used inconjunction with an occupancy sensor, such as the occupancy sensor 1described in relation to FIGS. 1 and 2.

In a further embodiment, an occupancy sensor, such as the occupancysensor 1 described in relation to FIGS. 1-4 may include ambient lightsensing capability and variable time of day functionality similar tothat described in relation to the embodiment of FIG. 5. With suchfunctionality, a photodetector associated with an occupancy sensor canbe used to modify functionality of the occupancy sensor.

For example, a photodetector may be employed to “hold off” turninglights on, even when the occupancy sensor determines that an area isoccupied, for cases in which the photosensor (or an associatedprocessor) determines that ambient lighting levels due to natural lightin the area are above a predetermined threshold. In some cases thispredetermined threshold may be a lighting value deemed adequate for anindividual to perform a particular activity in the associated space.

Recognizing that a desired threshold lighting level for a particularmonitored area may change based on the time of day (for any or all ofthe reasons previously noted), this “hold off” functionality, as well asother functionality, may be modified based on the time of day.

As will be appreciated, different work areas may be associated withtasks requiring different levels of light (either for comfort or safety)during working hours as compared to non-working hours. For example, in awarehouse during working hours, areas may be occupied with employeesmoving a wide variety of materials for shipment or which have beenreceived. In some cases this may include the use of manual or poweredmachinery (e.g., hand trucks, fork lifts) which, for safety reasons,require a relatively high lighting levels. After hours, the activitythat required enhanced lighting levels may cease, but the area may stillbe used by employees passing through on their way out of the building atthe end of the work day. Thus, in the after-hours period, naturaldaylight may provide adequate illumination to enable safe passage of theemployees out of the building, and thus, there may be no need to turnthe lights on during this time period, even where the occupancy sensordetermines that the area is occupied.

Another example can involve open cubicle work areas. During workinghours, relatively high lighting levels may be desired to enable workersto comfortably perform tasks. After hours, however, it may not benecessary to turn lights on in the area, as a few employees may passthrough these unoccupied areas as they leave for the day. Thus, thelighting level at which the occupancy sensor will “hold off” turning onthe lights can change for a particular area depending on the time of dayand the kind of work being performed in the area.

To implement this functionality, a plurality of different predeterminedlighting levels may be programmed into one or more of the photosensor,the occupancy sensor, and an associated processor. The predeterminedlighting levels may also be stored in non-volatile memory associatedwith the processor. The predetermined lighting levels may be employed tocustomize the “hold off” operation of the occupancy sensor to ensurethat the minimum required lighting level is maintained for an area,while also ensuring that lighting in excess of the minimum requiredlevel is not provided. As will be appreciated such a feature ensures asafe working light level while also minimizing energy consumption.

In one exemplary non-limiting embodiment, a first predetermined lightinglevel may be associated with normal working hours (e.g., 8:00 AM to 5:00PM) and may require a higher level of ambient light (i.e., daylight) inorder for the occupancy sensor to “hold off” energizing associated arealighting. A second predetermined lighting level may be associated withnon-working hours (e.g., 5:00 PM to 8:00 AM, weekends, holidays) thatmay require a lower level of ambient light in order for the occupancysensor to “hold off” energizing associated area lighting. One or moreadditional predetermined lighting levels (and predetermined hold-offs)may also be associated with other periods of time during the day (e.g.,lunch time) and/or days of the week, holidays and the like.

The disclosure thus describes systems and methods for changing thefunctionality of occupancy and/or lighting systems based on the time ofday. In some embodiments, the time of day is determined based on lightlevels sensed by an associated photodetector. In some embodiments, timeof day determinations are used to modify daylighting targets or ambientlight hold-offs.

Some embodiments of the disclosed device may be implemented, forexample, using a storage medium, a computer-readable medium or anarticle of manufacture which may store an instruction or a set ofinstructions that, if executed by a machine (i.e., processor ormicrocontroller), may cause the machine to perform a method and/oroperations in accordance with embodiments of the disclosure. By way ofexample, such a machine may include, but not limited to, any suitableprocessing platform, computing platform, computing device, processingdevice, computing system, processing system, computer, processor, or thelike, and may be implemented using any suitable combination of hardwareand/or software. The computer-readable medium or article may include,but not limited to, any suitable type of memory unit, memory device,memory article, memory medium, storage device, storage article, storagemedium and/or storage unit, for example, memory (including, but notlimited to, non-transitory memory), removable or non-removable media,erasable or non-erasable media, writeable or re-writeable media, digitalor analog media, hard disk, floppy disk, Compact Disk Read Only Memory(CD-ROM), Compact Disk Recordable (CD-R), Compact Disk Rewriteable(CD-RW), optical disk, magnetic media, magneto-optical media, removablememory cards or disks, various types of Digital Versatile Disk (DVD), atape, a cassette, or the like. The instructions may include any suitabletype of code, such as source code, compiled code, interpreted code,executable code, static code, dynamic code, encrypted code, and thelike, implemented using any suitable high-level, low-level,object-oriented, visual, compiled and/or interpreted programminglanguage.

While certain embodiments of the disclosure have been described herein,it is not intended that the disclosure be limited thereto, as it isintended that the disclosure be as broad in scope as the art will allowand that the specification be read likewise. Therefore, the abovedescription should not be construed as limiting, but merely asexemplifications of particular embodiments. Those skilled in the artwill envision additional modifications, features, and advantages withinthe scope and spirit of the claims appended hereto.

1. An occupancy sensor, comprising: a passive infrared (PIR) sensingelement; a temperature sensing element; and a processor coupled to thePIR sensing element and the temperature sensing element, the processorconfigured to receive temperature signals from the temperature sensingelement and to configure the occupancy sensor into a selected one of aplurality of operating modes based on the received temperature signals;the processor further configured to receive occupancy signals from thePIR sensing element and to control an associated load based on theselected operating mode and the received occupancy signals.
 2. Theoccupancy sensor of claim 1, wherein the processor associates each ofthe plurality of operating modes with at least one of: a differentsensing threshold of the PIR sensor, a different sensing threshold ofthe temperature sensing element, and a different time delay beforeturning off the associated load.
 3. The occupancy sensor of claim 1,wherein the processor is programmed to compare the received temperaturesignals to a first stored threshold value and to configure the occupancysensor into a first operating mode when the received temperature signalsexceed the first stored threshold value.
 4. The occupancy sensor ofclaim 3, wherein the processor is programmed to compare the receivedtemperature signals to a second stored threshold value and to configurethe occupancy sensor into a second operating mode when the receivedtemperature signals exceed the second stored threshold value, whereinthe second stored threshold value is greater than the first storedthreshold value.
 5. The occupancy sensor of claim 4, wherein when theoccupancy sensor is in the first operating mode a first sensingthreshold is associated with the PIR sensor, and wherein when theoccupancy sensor is in the second operating mode a second sensingthreshold is associated with the PIR sensor, wherein the first sensingthreshold is different than the second sensing threshold.
 6. Theoccupancy sensor of claim 1, wherein each of the plurality of operatingmodes is associated with a preselected sensing threshold associated withthe PIR sensor, at least two operating modes of the plurality ofoperating modes having a different preselected sensing threshold.
 7. Theoccupancy sensor of claim 6, wherein a first operating mode of theplurality of operating modes is associated with temperature signals thatexceed a first predetermined value, and a second operating mode of theplurality of operating modes is associated with temperature signals thatexceed a second predetermined value, the first predetermined valuerepresentative of a first ambient temperature, the second predeterminedvalue representative of a second ambient temperature, the first ambienttemperature lower than the second ambient temperature.
 8. The occupancysensor of claim 1, further comprising a memory associated with theprocessor, the memory for storing first and second predetermined valuesassociated with the selected operating mode.
 9. The occupancy sensor ofclaim 1, further comprising a photodetector coupled to the processor,the processor executing instructions for: receiving an ambient lightlevel signal from the photodetector, the ambient light level signalrepresentative of an ambient light level in a monitored area, comparingthe ambient light level signal to a first predetermined lighting levelassociated with a first time period, the first time period associatedwith a time of day, and controlling the associated load based on thecomparison.
 10. The occupancy sensor of claim 9, wherein when theambient light level signal is below the first predetermined lightinglevel during the first time period, controlling the associated loadcomprises increasing a brightness of the associated load until theambient light level signal is substantially equal to the firstpredetermined lighting level.
 11. The occupancy sensor of claim 9,wherein when the ambient light level signal is above the firstpredetermined lighting level during the first time period, controllingthe associated load comprises decreasing a brightness of the associatedload until the ambient light level signal is substantially equal to thefirst predetermined lighting level.
 12. An occupancy sensor, comprising:an occupancy sensing element; a photodetector; and a processor coupledto the occupancy sensing element and the photodetector, the processorconfigured to receive light signals from the photodetector and toconfigure the occupancy sensor into at least one of a plurality ofoperating modes based on an estimated time of day, the estimated time ofday determined by the processor based on selected ones of said lightsignals received from the photodetector; wherein the processor isconfigured to receive occupancy signals from the occupancy sensingelement and to control an associated load based on the selectedoperating mode and the received occupancy signals.
 13. The occupancysensor of claim 12, wherein the processor associates each of theplurality of operating modes with at least one of: a different sensingthreshold of the PIR sensor, a different sensing threshold of thetemperature sensing element, and a different time delay before turningoff the associated load.
 14. The occupancy sensor of claim 12, a firstoperating mode of the plurality of operating modes being selected by theprocessor when the light signals from the photodetector are determinedby the processor to be associated with a first lighting level associatedwith a first predetermined time of day; wherein when in the firstoperating mode the load is not energized regardless of whether theprocessor receives occupancy signals from the occupancy sensing element.15. The occupancy sensor of claim 14, a second operating mode of theplurality of operating modes being selected by the processor when thelight signals from the photodetector are determined by the processor tobe associated with a second lighting level associated with a secondpredetermined time of day that is different from said firstpredetermined time of day; wherein when in the second operating mode theload is energized when the processor receives occupancy signals from theoccupancy sensing element, the load being maintained in the energizedstate for a first predetermined time period.
 16. The occupancy sensor ofclaim 15, a third operating mode of the plurality of operating modesbeing selected by the processor when the processor determines, based onthe estimated time of day, that a third predetermined time of day hasbeen reached, the third predetermined time of day being different fromthe first and second predetermined times of day; wherein in the thirdoperating mode the load is energized when the processor receivesoccupancy signals from the occupancy sensing element, the load beingmaintained in an energized state for a second predetermined time period,the first predetermined time period being greater than the secondpredetermined time period.
 17. The occupancy sensor of claim 12, whereinthe estimated time of day is determined by the processor as being themidpoint time between a sunrise state and a sunset state, the sunrisestate associated with a first light threshold value and the sunset stateassociated with a second light threshold value, the processordetermining the sunrise state when light signals received from thephotodetector indicate an ambient light level greater than the firstlight threshold value, the processor determining the sunset state whenlight signals from the photodetector indicate an ambient light levelgreater than the second light threshold value.
 18. The occupancy sensorof claim 17, further comprising a memory associated with the processor,the memory for a sunrise time associated with said sunrise time, asunset time associated with said sunset time, the midpoint time and thepredetermined time of day.
 19. The occupancy sensor of claim 12, whereinthe occupancy sensing element is RF, PIR, ultrasonic, acoustic or videoelements, and combinations thereof.
 20. A method for controlling a loadwith an occupancy sensor, the method comprising: at a PIR sensor,identifying an occupied condition of a monitored area and sending anoccupancy signal to a processor; at a temperature sensing element,identifying an ambient temperature of the monitored area and sending atemperature signal to the processor representative of said ambienttemperature; at the processor, receiving the temperature signal andconfiguring the occupancy sensor into a selected one of a plurality ofoperating modes based thereon; and controlling a load associated withthe monitored area based on the selected operating mode and theoccupancy signal; wherein the selected operating mode is associated witha predetermined sensing threshold associated with the PIR sensor. 21.The method of claim 20, wherein configuring the occupancy sensor into aselected one of a plurality of operating modes comprises comparing thetemperature signal to a first stored threshold value and configuring theoccupancy sensor into a first operating mode when the temperaturesignals exceed the first stored threshold value.
 22. The method of claim21, wherein configuring the occupancy sensor into a selected one of aplurality of operating modes comprises comparing the temperature signalsto a second stored threshold value and configuring the occupancy sensorinto a second operating mode when the temperature signals exceed thesecond stored threshold value.
 23. The method of claim 20, wherein whenthe occupancy sensor is in a first operating mode of the plurality ofoperating modes a first sensing threshold is associated with the PIRsensor, and wherein when the occupancy sensor is in a second operatingmode of the plurality of operating modes a second sensing threshold isassociated with the PIR sensor, wherein the first sensing threshold isdifferent than the second sensing threshold.
 24. The method of claim 20,wherein each of the plurality of operating modes is associated with apreselected sensing threshold associated with the PIR sensor, at leasttwo operating modes of the plurality of operating modes having adifferent preselected sensing threshold.
 25. A method for controlling aload with an occupancy sensor, the method comprising: at an occupancysensing element, identifying an occupied condition of a monitored areaand sending an occupancy signal to a processor; at a photodetector,identifying an ambient light level of the monitored area and sending alight signal to the processor representative of said ambient lightlevel; at the processor, receiving the light signals from thephotodetector and configuring the occupancy sensor into at least one ofa plurality of operating modes based on an estimated time of day, theestimated time of day determined by the processor based on selected onesof said light signals received from the photodetector; and controlling aload associated with the monitored area based on the selected operatingmode and the occupancy signal.
 26. The method of claim 25, whereinconfiguring the occupancy sensor into at least one of a plurality ofoperating modes comprises configuring the occupancy sensor into a firstoperating mode when the light signals from the photodetector aredetermined to be associated with a first predetermined time of day; andwherein when in the first operating mode the load is not energizedregardless of whether the occupancy signal is received from theoccupancy sensing element.
 27. The method of claim 26, whereinconfiguring the occupancy sensor into at least one of a plurality ofoperating modes comprises configuring the occupancy sensor into a secondoperating mode when the light signals from the photodetector aredetermined to be associated with a second predetermined time of day thatis different from said first predetermined time of day; and wherein whenin the second operating mode the load is energized when the processorreceives occupancy signals from the occupancy sensing element, the loadbeing maintained in the energized state for a first predetermined timeperiod.
 28. The method of claim 27, wherein configuring the occupancysensor into at least one of a plurality of operating modes comprisesconfiguring the occupancy sensor into a third operating mode when theprocessor determines, based on the estimated time of day, that apredetermined time of day has been reached; wherein in the thirdoperating mode the load is energized when the processor receivesoccupancy signals from the occupancy sensing element, the load beingmaintained in an energized state for a second predetermined time period,the first predetermined time period being greater than the secondpredetermined time period.
 29. The method of claim 28, furthercomprising, at the processor, determining the estimated time of day asthe midpoint time between a sunrise state and a sunset state, thesunrise state associated with a first light threshold value and thesunset state associated with a second light threshold value, theprocessor determining the sunrise state when light signals received fromthe photodetector indicate an ambient light level greater than the firstlight threshold value, the processor determining the sunset state whenlight signals from the photodetector indicate an ambient light levelgreater than the second light threshold value.